Communities (online or offline) are people interacting and building relationships around topics of interest. It shouldn't be a surprise when they mourn the loss of popular members, help to support each other, and rally around causes they hold dear.

Does the medium change the meaningfulness of the community?

My advice, treat online communities like offline communities.

Imagine these people live around your area. Which tactics would you still use? How would you get people to interact? How would you build and solidify relationships? How would you engage people in the first place?

The same tactics that work in the real world are remarkably resilient online too. The more you push for real-time activities, personal interactions between members, common goals/causes, community-orientated content, the more likely you will develop a genuine community.